Devices used to hold substrates, such as semiconductor wafers, flat panel displays, recording head or other similar type of substrates, are commonly referred to as chucks. Chucks are used to hold substrates during processing as well as inspection. Chucks commonly hold a substrate gravitationally, electromagnetically, through the use of a vacuum or by clamping the top and bottom of the substrate at the edge of the substrate.
During inspection of a substrate, the chuck typically is required to move the substrate under the optics of the metrology equipment. It is desirable to move the substrate quickly during inspection to improve throughput. Thus, the substrate should be held securely so that movement of the chuck will not displace the substrate. However, the substrate should be held safely so as to not damage the substrate.
Some substrates, e.g., semiconductor wafers, are very sensitive to environmental conditions. Accordingly, during processing, it is often desirable to inspect a substrate without altering the environmental conditions, e.g., the substrate could be measured within the processing chamber. When inspection of a substrate is to be performed within a chamber at a particular pressure, e.g., in a vacuum, the type of chuck used to secure the substrate is limited. For example, vacuum chucks, as well as pneumatic or vacuum activated clamping chucks, cannot be used in a vacuum environment. Moreover, the space within the chamber is generally limited and, thus, the chuck should have a compact design.
Thus, what is needed is a compact chuck that can safely and securely hold a substrate in various environmental conditions.